This invention relates to a terminal box for housing electrical connections and components in underground cable transmission systems.
A principal use of the terminal box of this invention is in connection with telephone cables which have a large number of conductors which provide telephone or other communication services. When such cables are run underground, they are periodically brought above ground into terminal boxes of the type disclosed herein. In the terminal boxes, the cable jackets are removed, and individual conductors are spliced to outgoing cables or are terminated by being electrically connected to conductors which lead to the individual customers in the vicinity of the loop. The above-ground cable portion is usually an inverted U-shaped loop, but in some instances it will have only one leg, the individual conductor then being connected to various types of termination devices which are electrically connected to the customers being served.
The principal structural components of the terminal box of this invention are similar to those of existing terminal boxes, in the respect that a pair of mutually facing upright channels have overlapping vertical margin portions, with one of the channels carrying a cap which forms the top of the terminal box.
Terminal boxes are normally installed with their lowr ends buried several inches in the ground, their upper portions extending above the ground and exposed to the weather. These exposed conditions create a number of problems, the solutions to which are believed to be offered by the invention disclosed herein. One such problem is corrosion of the underground parts of a metallic terminal box. Another problem is that the interior of a terminal box may be invaded by insects, animals, dust and undesired amounts of moisture. Other problems are attributable to the fact that grass often grows very close to the terminal box. This leads to fire damage in the event of a grass fire, and impact damage when lawnmowers are continually brought into contact with the exterior surface of the terminal box.
The prior art also presents some problems with respect to the installation and maintenance of a terminal box and its enclosed electrical components. One inconvenience is caused by sheets of dielectric material which are wrapped around the components within the terminal box. These sheets are a source of annoyance to workers who for convenience have been known to remove these protective sheets, thus increasing the risk of an electrical short against the walls of the metallic terminal box. Another problem relates to vertical guides or passages in the lower portion of the terminal box for accommodating incoming and outgoing conductors. Conventionally, such passages are located at only one position on the housing, thus requiring the line to be fed to that particular position, and imposing substantial problems when it is necessary to replace part or all of the terminal box. Another practical problem arises when a terminal box is of insufficient size to accommodate the electrical components needed to serve the locality of the terminal box.
The object of the terminal box constructed according to the preferred embodiment of the invention is to avoid all of the foregoing problems in a simple, safe and effective assembly. The preferred embodiment disclosed herein utilizes a number of features, many of which may be used singly, but which collectively provide a terminal box which is convenient to install and modify, is resistant to corrosion of the buried portions thereof, is less likely to be damaged by lawnmowers, small vehicles or grass fires, may be serviced without tampering with the interiorily positioned dielectric sheet material, and excludes insects, animals, dust and undue moisture while still permitting ambient air to communicate with the interior of the housing.
An extremely important durability feature of the improved terminal box is the provision of a corrosion-avoidance system wherein a metallic terminal box is electrically connected to a buried piece of metal which, in the EMF series, is anodic to the metal of the terminal box.
An integrity-providing feature of the preferred embodiment of the invention is the pressure of a cap assembly provided with an insect-excluding seal located in the space between th cap and the housing member which is separable from the cap. This seal is air-permeable but it filters out undesired particulate contaminants such as dust, rain, snow and sand.
Another integrity-providing feature of the preferred embodiment of the invention is the use of a resilient strip to deter the entry of dust, rain or blowing snow into the splicing area of the housing. This strip is attached to one of the channels which forms the housing and is located where the front and rear channels of the terminal box overlie each other.
A third integrity-providing feature of the preferred embodiment of the invention results from a continuous barrier sheet located in the terminal box approximately at ground level to prevent upward entry into the splicing area of undue moisture, snakes and rodents. This barrier sheet may be cut by ordinary hand tools such as knives or scissors, and it is provided with support means for engaging the interior walls of the terminal box. A caulking or adhesive sealant assures the integrity of the barrier formed by this sheet.
A protective feature of the terminal box constructed according to the preferred embodiment of the invention, is the addition of a contiuous vegetation-inhibiting sheet surrounding the base of the terminal box at ground level to prevent grass and other vegetation from growing close to the terminal box. This reduces the likelihood that the terminal box will be struck by lawnmowers, it will increase the visibility of the terminal box at ground level for other small vehicles, and it will reduce the risk of damage to the terminal box contents in the event of grass fires.
A convenience feature of the invention is that the terminal box may be enlarged so as to accommodate electrical components which are larger in size or number. The terminal box is volumetrically expansible by replacing the removable channel members with channels which have deeper side flanges and thus provide a greater depth. This feature will provide for a substantial savings in maintenance and construction costs.
Another convenience feature according to the preferred embodiment of the invention is the attachment of a piece of dielectric material to the removable cover of the terminal box, and the attachment of a second piece of dielectric material to the stationary part of the terminal box, with the sheets overlapping in the area where the removable and stationary parts of the terminal box are interconnected. This arrangement prevents the establishment of undesired electrical contact between the grounded terminal box and its contents.
Still another convenience-motivated feature of the preferred embodiment of the invention is the provision in the lower section of the terminal box of a conductor guide passage through which conductors enter the lower end of the terminal box, the improvement of this feature being that the passageforming element is removably attached at one corner of the housing and is capable of being removably attached to any of the other corners of the housing to meet the exigencies of the particular terminal box installation.